The present invention relates to air vent valves for steam radiators, and more particularly, to improved syphon tubes for use with such air vent valves.
Steam heating systems which include radiators commonly include air vent valves connected to the radiators by means of a threaded valve nipple. When the heating system is energized, excess air in the system is vented through the nipple of the air vent valve, past a liquid-filler float, and out through an opening near the top of the valve. When steam from the radiator enters the valve, the liquid in the float expands, causing the float to seal the vent opening, then when the heating system is de-energized, the radiator and vent valve gradually cool, causing the steam in the vent valve to condense.
It has been well known in the art to provide a syphon tube having one end inserted into the valve nipple and the other end disposed within the radiator, so that when the level of condensate in the vent valve rises to the level of the valve nipple, the syphon tube will drain the condensate back into the radiator.
The syphon tube which has been in common use is a formed copper tube and the end disposed within the valve nipple is flared or enlarged in some other manner to prevent the tube from being withdrawn from the valve nipple. Therefore, the upstream portion of the tube is normally horizontal, the tube includes about a 90.degree. bend and the downstream portion of the tube is oriented downwardly to direct the flow of condensate downward into the radiator. The formed copper syphon tube presently known in the art has the distinct disadvantage of having to be inserted through the valve nipple from the inside of the vent valve before final assembly of the valve. Thus, during subsequent assembly, testing and handling of the assembled vent valve, the syphon tube is already in place and frequently becomes damaged, such as by being bent to the extent that the interior passage defined by the copper tube is pinched off, preventing fluid flow therethrough. If sufficient damage occurs to the syphon tube, the entire vent valve assembly must be scrapped.
Accordingly, it is an object of the present invention to provide a vent valve assembly in which the syphon tube may be inserted after final assembly of the vent valve, to facilitate subsequent testing, handling and shipping of the vent valve and syphon tube assembly.
It is a related object of the present invention to provide a vent valve assembly in which the syphon tube may be snapped in place within the valve nipple at any time, such as at installation of the vent valve assembly to the radiator.
Another type of vent valve syphon tube is illustrated in U. S. Pat. No. 3,583,481, assigned to the assignee of the present invention. In the illustrated vent valve assembly, the syphon tube comprises a flexible tube (rubber or plastic) having a flared insert within the upstream portion of the tube to hold it in place within the valve nipple, and a weighted tube insert at the downstream end of the tube to cause it to bend downward within the radiator, directing the flow of condensate downward. Although the syphon tube of the above-identified patent has some degree of flexibility, it suffers from the same disadvantage as the presently used copper syphon tube; i.e., it must be inserted through the valve nipple before final assembly of the vent valve. In addition, the three piece configuration of the flexible syphon tube complicates the manufacturing and assembly of the valve and adds unnecessary manufacturing expense thereto.
Accordingly, it is an object of the present invention to provide a vent valve assembly which achieves the above-stated objects, and in which the syphon tube is of such a configuration that it may be fabricated, such as by injection molding, as a single piece.